Until the time of the Lord’s atoning sacrifice was made in the flesh, faithfulness to that portion of the law of Moses prescribed by the prophets was prerequisite to divine approbation. Elder Bruce R. McConkie has written:
“We cannot always tell ... whether specific sacrificial rites performed in Israel were part of the Mosaic system or whether they were the same ordinances performed by Adam and Abraham as part of the gospel law itself. Further, it appears that some of the ritualistic performances varied from time to time, according to the special needs of the people and the changing circumstances in which they found themselves. Even the Book of Mormon does not help us in these respects. We know the Nephites offered sacrifices and kept the law of Moses. Since they held the Melchizedek Priesthood and there were no Levites among them, we suppose their sacrifices were those that antedated the ministry of Moses and that, since they had the fulness of the gospel itself, they kept the law of Moses in the sense that they conformed to its myriad moral principles and its endless ethical restrictions. We suppose this would be one of the reasons why Nephi was able to say, ’The law hath become dead unto us.’ (2 Nephi 25:25.) There is, at least, no intimation in the Book of Mormon that the Nephites offered the daily sacrifices required by the law or that they held the various feasts that were part of the religious life of their Old World kinsmen.” (Promised Messiah, p. 427, italics added.) See also Commentary 1:296-97; 2:34-35, 210.